Row crops, as sugar beets, must be thinned and weeded to provide growing conditions that result in maximum yields. Row crop cultivators, as shown in U.S. Pat. Nos. 3,680,648, are used to cultivate the ground between the rows to control weeds. These cultivators do not remove or control the weeds in the rows. Herbicides are used for weed control in the rows. An example of an herbicide incorporator is shown in U.S. Pat. No. 3,741,137. Notwithstanding the application of herbicides and between row cultivation, weeds such as pig weed, lamb's quarters, mustard and the like, are still found in beet fields. Hand laborers using hoes work the fields to thin the beets and remove the unwanted weeds. The hand labor is time consuming and costly.
Machines for pulling stalks out of the ground have been known since 1872. Merriman in U.S. Pat. No. 133,110 describes a machine for pulling cotton stalks out of the ground. This machine has two rollers biased together and driven by ground engaging wheels. Similar machines are disclosed by Jones in U.S. Pat. No. 1,379,571 and Bailey in U.S. Pat. No. 1,821,131. Both of these machines have two pairs of rollers driven by separate ground wheels. The same stalks are pulled by both rollers. Tucker describes in U.S. Pat. No. 2,066,864 a cotton stalk pulling machine having two rolls driven by ground wheels. A separate frame carrying a ground engaging wheel is used to rotatably support the rolls. Barrentine in U.s. Pat. No. 3,437,152 has two pairs of rollers operable by a power takeoff drive to pull two rows of cotton stalks. The pulled stalks are cut with rotary knives before they are discharged back to the ground.